The challenge of protecting strategic enclosures and desolated long border lines is known from days yore. Partly, the problem is alleviated by erecting a physical barrier means around the perimeter of the enclosure or along the border line—for example by building a massive wall or by deploying a robust fence means or other known similar means.
Also well known are systems for detecting attempts to overcome such barriers that are performed by penetrating through the physical barrier means or climbing and crossing over it. These systems generate and send suitable warning signals in real time to a remote control center, providing also the location (to within a limited accuracy) of the whereabouts of the attempted break in.
Such systems comprise an array containing plurality of sensors (dubbed multi sensors array) that is deployed along the physical barrier means and linked to it in a manner that enables sensing via the array, of one or more occurrence/s (or in other words—typical phenomena), that takes place when there is an attempted penetration through the physical barrier means or by climbing on and over it and generating (producing) an indication when such an occurrence is actually sensed.
For example—
An array of sensors such that those that are close to the attempted penetration location sense the occurrence of vibrations and shocks that naturally accompany the breaking in and cutting of the grid (in a grid type of physical barrier), or, another example—
An array of sensors that, once more, are adjacent to the site of the incident and “feel” (detect) the phenomena of variations in the tension of the wires, that naturally accompanies cutting, sawing of—or climbing on—the taut stretched wires (when the physical barrier means is a taut wires type of fence).
When sensing an attempted penetration as said, a transmission means that is coupled to the sensors array routes and leads the indications generated by the sensor/s (one or more) that are adjacent to the site of the incident to a remote locality (point), unto a control center that receives the indication and in its turn generates—at times after performing first an analysis of the received indication and subject to it, a warning reporting the occurrence of an attempted intrusion, through the above cited physical barrier or by climbing on and over it.
Such systems and sensor means that serve in them where published and described in the past, including—as well, in documents of old patents. For example—
U.S. Pat. No. 4,829,287 of Kerr et al, that described in a taut wire type of intrusion detection system, a system wherein each parallel wire defines a section of a security fence and is tensioned between a pair of wire-supporting vertical anchor posts. Intermediate the anchor posts there is provided in accordance to Kerr's patent, a row of regularly spaced vertical detector posts each presenting a plurality of individual sensors, each associated with one of the taut stretched wires and operable to produce a sensor's signal when the tension of the wires changes. With each detector post there is associated sensor signal processing means, operable to analyze the sensor signals produced by the sensors of the detector post in response to changes in tension of the taut wires, and to generate output signals correlatable with the sensor signals. Each sensor preferably includes additionally a pressure transducer comprising a partially conductive compressible elastic sensing element whose resistance changes with applied pressure.
U.S. Pat. No 5,103,207—also of Kerr et al, describes a sensor post formed with a hollow interior and a semi-rigid surface which flexes in response to an applied force. Sensor bars are mounted to the semi-rigid surface in a cantilevered fashion, and include an intermediate electrically insulated section located inside the interior of the sensor post. The sensor element mounting means is rigidly mounted to a portion of the sensor post which remains essentially stationary during an intrusive event. Sensing elements are made of a flexible semi-conductive sensing material, whose resistance increases when the material is stretched, and are mounted so as to straddle an electrically insulated section of the sensor bars. A signal analysis means detects an increase in the resistance of the sensing elements and generates an alarm. A wire guiding device uses a separator bar shaped into a zig-zag configuration which is provided with a series of apertures forming an axial channel, and a locking rod dimensioned for insertion into the axial channel formed in the separator bar, thereby entrapping the taut wires.
U.S. Pat. No. 5,329,027 of Brunot et al, described a taut wire perimeter fence intrusion detection system. The taut wire deflection sensors in the system each include a flexible housing into which is disposed a full resistance bridge having strain gages for each leg. Opposing strain gages in the bridge circuit have predominant directions in common directions. The strain gages are formed directly onto a printed circuit board. An amplifier circuit is also mounted onto the circuit board, for amplifying the differential bridge voltage from the bridge. The taut wire is connected to the housing, for example by way of a slotted bolt and nut, so that horizontal deflection of the taut wire creates strain on the circuit board which is sensed by the strain gage bridge, amplified by the amplifier, and communicated to a data processing system which generates the appropriate alarm condition.
U.S. Pat. No. 5,602,534 of Granat described a sensor for use in an electrical security fence, comprising an electrically conductive housing completely enveloping an electronic component so as to screen the electronic component from electromagnetic radiation whilst permitting movement of the electronic component relative to the housing when acted upon by an external force. According to a preferred embodiment, the electronic component is a deflection sensor or taut wire sensor, such that the sensor is completely shielded from the atmospheric effects and stray radiation.
Buckley et al, in U.S. Pat. No. 6,646,653 described a deflection sensor for a taut wire perimeter fence detection system, which can be installed after the fence wire has been installed easily, and the sensor that operates in line with the wire tension. The sensor includes a plate member adapted to be pivotally mounted, a first wire attachment point at one end of said plate member, a second wire attachment point remote from said first wire attachment point and a transducer or sensor element located on said plate member between the attachment points. The taut wire type detection system including at least one taut wire for a perimeter fence supported by a plurality of posts, at least one deflection sensor being pivotally mounted to one of the posts or a support thereon and a sensor processing circuit for interrogating the at least one deflection sensor and to provide an alarm indication on tampering of the at least one taut wire or the at Yeast one deflection sensor.
U.S. Pat. No. 6,737,972 of Gitlis, described a vibration sensor that is used in conjunction with perimeter security systems. The sensor is comprised of two conductive spherical elements each resting on a pair of parallel conductive arcs. A plurality of sensors are attached to mounting device and placed at spaced intervals on a security fence. The sensors are used to detect persons who attempt to cut, climb, lift, or contact the security fence.
However, these prior art systems suffer from a number of disadvantages. Primary among those are—
Lack of immediate capability to perform calibrations and alterations of the thresholds of sensitivity, individually—both individual and specific—of the sensor units, let alone perform it remotely (from the control system), without having to approach the sensor or to physically open or dismantle it.
In other words, systems in accordance with the prior art are not decentralized from the point of view of the control and command (availability) over the sensor components that are assembled in them.
Sensors in accordance with the known prior art do not include, each one of them a processing component (for example—a component of the micro processor type), individually of his own, and hence, they do not enable, for example—remotely approaching each individual sensor with specific commands and/or data, implementation of an individual and specific algorithm in each one of them, nor dividing the protected area into sectors with different sensitivities or performing variations in the calibrations at the specific sensor (unique) level.
This means that there exists a deficiency that causes, of course—a reduction in the available sensitivity in said systems that are in accordance with the prior art, and as a consequence, also disrupts (harms) their reliability.
An additional drawback found in earlier systems as per prior art documentation, is the inability to perform serviceability tests while employing a self excitation method remotely in order to generate the same phenomena themselves as the sensor unit does actually sense when an attempted penetration act is being made. This is rather performed today in the cumbersome—and at times even dangerous way of sending a person to rock, bend or shake the various fence sectors.
Yet another drawback found in earlier systems as per the prior art, is the lack of ability to integrate several types of sensors—such that they implement various detection technologies different from one another, rendering the system to be an integral system operating over a single communication line.
Systems as per the prior art are characterized by the uniformity from the aspect of the sensors types that are installed in them, and by lack of diversity and combinations of applying several types of sensors into one system (wherein each addition of a sensors type mandates the need to add a dedicated, special transmission line for it).
Obviously, such uniformity exposes the system to relatively easy trials to disrupt it—as then the intruder has to cope with only one kind of sensor that he has to overcome (or neutralize).
The complexity that is thus forced on systems as per prior art, as said, renders the system to be more expensive and also adds to its constructional and maintenance complexity.
Systems as per prior art, do not provide the capability of easy and convenient available (accessible) interfacing with commercial alarm systems that abound in the market (for example in the private or industrial markets). The customer might desire to integrate the system with an existing commercial alarm system in his disposal, and this ability is not offered by systems that are as per the above cited prior art.